Playground balls are rubber balls which are soft and pliable because they have no carcass, i.e., no nylon-wound bladder. Playground balls are primarily used for bouncing, catching and bombardment-type activities. They are widely used by schools, recreation facilities and physical therapists. Playground balls are specifically designed for inflation to a particular diameter. Individual playground balls which are specifically designed for each of four, five, six, seven, eight and one-half, ten, thirteen and sixteen inch inflation, are common.
Because playground balls have no nylon wound bladder there is nothing to stop them from being over-inflated and it is very common that playground balls become over-inflated. When a playground ball is over-inflated, the seams tend to spread and the lifetime of the ball is drastically reduced. Severe over-inflation could even cause explosion of the ball upon impact which, of course, is not very desirable among young children. Under-inflation is also a problem as unless fully inflated the ball will not bounce correctly.
Achieving proper inflation of a playground ball has been a major difficulty to the present time. Generally, the problem is ignored, resulting in common over-inflation and substantial diminishment of the life of playground balls. Even when the problem is not ignored, the amount of inflation can only be roughly estimated, perhaps by placing the ball upon a ruler and looking at it from above in order to estimate the diameter to which it has been inflated. This is very difficult and inaccurate. No device is presently on the market which addresses this problem.